Conventional techniques for forming a film on a substrate include a “spray method” and a “mist method.” The “spray method” involves spraying droplets of approximately 10 μm to 100 μm in diameter onto a substrate. The “mist method” involves misting droplets of approximately several micrometers in diameter onto a substrate.
The spray method typically uses a two-fluid spray nozzle that bombards a solution with gas to transform the solution into droplets of approximately several ten micrometers in diameter. On the other hand, the mist method uses, for example, an ultrasonic vibrator to transform a solution into a mist of fine droplets of approximately several micrometers in diameter, and conveys the solution in mist form through a long pipe to a reaction chamber where a substrate is placed (or to a mist outlet).
One example of prior art literature on the spray method is Patent Document 1, and one example of prior art literature on the mist method is Patent Document 2.